Embodiments described below relate to process field devices. In particular, the embodiments relate to turbine flow meters.
In process environments, turbine flow meters, such as turbine flow meter 100 shown in sectional view in FIG. 1, provide a signal indicative of the flow of a fluid through a conduit 102. A typical turbine flow meter 100 includes a housing 104 with flanges 106 and 108 that are mounted to respective conduit sections 109 and 110. Within housing 104, hanger blades, such as hanger blades 112 and 114, support a hanger hub 116 that in turn supports an upstream cone 118, a downstream cone 120 and a rotor assembly 122. Rotor assembly 122 rotates freely around hanger hub 116 and includes a plurality of blades that are driven by fluid flowing through housing 104. In some meters, each of the blades of rotor assembly 122 includes a magnetic or paramagnetic material that is capable of generating an electric field in a pick-off coil 124 as the blade passes by pick-off coil 124. In particular, each blade creates a positive going voltage followed by a negative going voltage as it passes pick-off coil 124. In other meters, the magnetic material is located on other parts of rotor assembly 122.
As the flow rate increases, the angular velocity of rotor assembly 122 increases thereby increasing the frequency of the pulses generated by pick-off coil 124. The proportionality of the frequency of the pulses to the flow rate is dependent on the blade construction including the angle of the blades relative to the flow.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background.